Automatic audio-visual program control apparatus

ABSTRACT

There is disclosed an audio-visual program control apparatus for use in multi-media presentation that employ various audio and visual display devices as auxiliary units. The control apparatus provides coded cue signals to a high fidelity tape recorder in a pulse position modulated mode. These recorded cue signals are thereafter played back and decoded for automatic simultaneous operation of a plurality of display devices that operate at predetermined times in step with an audio program recorded on the tape. The control apparatus eliminates the disruptive effects of (1) distortion of the multiplex signals inherent in the tape recorder, and (2) electronic noise generated by the controlled display devices or similar nearby apparatus.

United States Patent 1 Parham Nov. 13, 1973 1 AUTOMATIC AUDIO-VISUAL PROGRAM CONTROL APPARATUS [76] Inventor: Darryl V. Pal-ham, 736 Newberry,

[52] U.S. Cl. l79/100.2 S, 179/1002 MD, 329/107,

332/9 T [51] Int. Cl. G03b 31/00, H03k 7/08 [58] Field of Search 179/1002 S, 100.2 MD; 332/9 R, 9 T, 11; 329/107; 328/119; 307/305 [56] References Cited UNlTED STATES PATENTS 3,480,738 11/1969 Meyer et a1. 179/1002 S 3,277,246 10/1966 Altonjl 179/1002 S 2,837,719 6/1958 Albanese 332/9 R 3,505,609 4/1970 -Vars0s 329/107 2,892,900 6/1959 Guttwein 179/1002 S 3,296,385 1/1967 Shaw 179/100.2 S

OTHER PUBLICATIONS v General Electric Application Note 90.16, 6/64 Silicon Controlled Switches," R. A. Stasior.

Primary Examiner-Bernard Konick Assistant Examiner-Jay P. Lucas Att0rney Giles C. Clegg, Jr., Jack A. Kanz and Richard E. Bee

[57] ABSTRACT There is disclosed an audio-visual program control apparatus for use in multi-media presentation that employ various audio and visual display devices as auxiliary units. The control apparatus provides coded cue signals to a high fidelity tape recorder in a pulse position modulated mode. These recorded cue signals are thereafter played back and decoded for automatic simultaneous operation of a plurality of display devices that operate at predetermined times in step with an audio program recorded on the tapejThe control apparatus eliminates the disruptive effects of (1) distortion of the multiplex signals inherent in the tape recorder, and (2) electronic noise generated by the controlled display devices or similar nearby apparatus.

21 Claims, 24 Drawing Figures I2 36 24 AUDIO PJ TAPE DECK INPUT- OUTPUT CUE |O ENCODER 33 1/ O A 4 221 -l PROJECTOR NO.1 1

PROJECTOR NO. 2 1

(3 l8 CUE i 3 DECODER PROJECTOR NO. 1

AUDIO EFFECTS 1 30- 9 Q E LIGHTING EFFECTS PATENTEDNBY 131975 3.772.473

SHEET 10F 4 12' 36 24 AUDIO TAPE DECK lNPUT OUTPUT CUE ENCODER 33 o IID H PROJECTOR NO! 1 0 -L PROJECTOR NO. 2 C l8 CUE DECODER PROJECTOR NO. 3 ,9 'L AUDIO EFFECTS V 30 f 2 Q m LIGHTING EFFECTS 22 3| 32 P 26 I FIG. I

x T Y T T I 1 5/ l iz BA T gFg L DELAY DELAY DELAY DELAY DELAY 1 FIG. ADD

SABCDE sABcDE FIG.2A

L FRAME J 20 MS. fil FIG. 2B

. s A B 0 DE s A B 0 DE FIC12C sA B c D E sA B c DE FIG. 2D

DARRYL v. PARH AM INVENTOR ATTORNEYS FIC13C F|G.3D

FICBBE PATENTEUIwv 13 I973 3.772.473

SHEET F 4 INPUT 64 74 I 54 3 H 84 93 m3 n4 5 F ss ONE *ADD 'INTEGRATE +DRIVER CUE Ta AGC F SHOT COUPLER L S T [72 r82 2 1 ||2 ONE CUE $5 SHOT ADD INTEGRATEbDRlVERt+ Bo SYNC F N r r r 2 r ONE CUE SEPARATOR ss SHOT ADD |NTEGRATE DRIVERI; COUPLER c X Y N r58 r68 1 V V F ss ONE ADD +INTEGRATE DRIVER CUE B t SHOT COUPLER N [56 r66 2 2 ONE CUE ss SHOT ADD INTEGRATE DRIVER COUPLER i T r uOVERRIDE Eng? LEVEL MC3ITOR ,BO ssc 55b 55d FIG-3A SABCDE SABCDE AGCOUTPUT s. SPOUTPUT F is. 35m L] (NO ONE-SHOT OUTPUT S. S. OUTPUT (FOR CUE) ADD CIRCUIT OUTPUT (FOR cuE) v DARRY L V. PA RHAM I N VEN TOR ATTORNE Y5 PATENIEU IIIIII I 3 I975 SHEET u 0F 4 CUE I626 ENCODER T -249 FIG. 9A

| I I H F. osc GATE MIxER- RECORD TRACK l I I72 i I68 I I l AUDIO INPUT-P I PJ {WW0 FIG. 9

L I640 F Z 1 I74 I76 I80 I82 I 5 4 i RECORDER I HIGH-BOOST NOTCH LOW-BOOST INPUT I FILTER P FILTER LTE T i I I J l I I L TUNED SAT. I CUE FIG IO: AMPLIFIER DRIVER I DECODER I I I I I "I? f* l FIG. IOA WI'MWr MONO TAPE MONO TAPE FIG. ICDB W RECORDER RECORDER E Iss0 l86b MULTIPLEX SIGNAL 0.0. E OUTPUT MIXER SEPARATOR AMP SWITCH 5 L I I62 5 J I64 192 90 AUDIO c I 1 |G.| l I88 'FROM FIG. 6A

I46 I O 6 I49 Am I48 DRlVER@m/ OUTPUT I LI I49 DARRYL V. PARHAM INVENTOR ATTORNEYS AUTOMATIC AUDIO-VISUAL PROGRAM CONTROL APPARATUS BACKGROUND AND SUMMARY OF TH INVENTION This invention relates to program control apparatus generally and more particularly to automatic audiovisual control apparatus for use in multi-media presentation.

In the presentation of educational lectures, fashion shows, art exhibits, theatrical performances or the like, it is extremely desirable to accompany the prerecorded audio portion'of the presentation with various visual effects that operate at a predetermined time, such as, coordinated lighting, slides or movie presentations, or sound effects to go therewith and to accompany same. in the past, however, in presenting demonstrations of the sort, various mechanical methods were used to control one display device. Most of these involved mutilation of the tape itself, i.e., cutting notches, applying conductive coating, or punching holes, which then made the tape useless for any other recording and very difficult to duplicate for mass distribution. A variation on this method uses punched paper tape or punched cards with holes as the cues storage means which tape or cards are advanced one set of holes at a time by a tape recorder. These various mechanical methods still only had one channel of tape control information and if more than one effect had to be controlled then a stepper relay or a similar apparatus had to be used. The auxiliary devices could not be controlled simultaneously. Overlooking the obvious reliability problems of detecting these mechanical cues with a switch or feeler wire, it is very difficult to program this type of apparatus for there is no way for the operator to view the results of the cues in real time. What was needed and is disclosed herein is an inexpensive correctable magnetic tape system which will store the coded cue signals and replay them to provide a multi-media show without relying on mechanical devices to provide a plurality of controlled auxiliary effects. However, recording of complex signals on magnetic tape is a formidable task and in the past apparatus for doing this tended to be very bulky and expensive making them unsuitablefor most audio-visual applications. It is the primary object of this invention to provide an inexpensive and reliable multiplexing system for audiovisual multi-media presentation that is small and portable and utilizes standard home entertainment magnetic tape deck equipment.

In accordance with the primary object of this invention, there is provided an audio-visual display system including a control unit which comprises a cue encoder-decoder which cooperates with the ordinary home entertainment type tape recorder and common auxiliary visual and audio display devices such as movie projectors, lighting units or phonographic recorders to provide a correlated presentation of the audio and vi sual material. One channel of the stereo tape recorder provides the primary audio portion of the presentation. On the other channel, a series of cue signals for operation of the auxiliary display devices is provided by the encoder during the programming of the master tape. Then, during presentation, it is merely required that the primary audio portion of the lecture be played off one track of the stereo tapedeck and the other track automatically provides signals to the control unit for decoding. The cue signals from this second track then switch or control a plurality of auxiliary units in a synchronous correlated manner to complete the presentation. If a mistake is made, during the programming of the master tape, the tape is simply stopped and is easily erased and changed without reviewing the entire program.

One of the inherent problems to overcome in simultaneous presentation of multiple effects by the foregoing system, is the normal tape recorder distortion, i.e., signal dropout or flutter, caused by the tape head or magnetic tape oxide irregularities which interrupt the decoding process. It is an object of this invention to provide a system having distortion immunity. It is another object of this invention to provide a system which continuously monitors the incoming pulse position modulated cue signals and trips an alarm if the signal deteriorates beyond a certain predetermined safe level. This monitor then automatically warns of tape breakage and day-to-day wear on recorder heads. and tapes.

It is a further object of this invention to provide a decoding circuit which separates the cue signals and directs the separated signals to individual cue comparison units for control of a plurality of auxiliary units in either a continuous or stepping mode.

It is another object of this invention to provide a system that can be selectively actuated by an operator while listening to the prerecorded audio program material. This system will then generate the coded cue signals and send both the audio and cue signals to the tape deck and to the decoding circuit so that the operator can both see and hear the result of his programming instantly. The operator is, in effect, performing the multimedia show in real time during the programming of the master tape.

It is another object of the invention to provide a cue coupling device which separates the electrical noise generated by the controlled auxiliary devices and similar apparatus from the decoding process, thereby preventing disruptive effects caused by ground loops or signal conductors.

It is a still further object of the invention toprovide a cue pulse width comparison circuit for each of these selectively actuated cue channels to monitor the time between the multiplexed pulses as the basic cue information. When the length of time exceeds a certain value for a certain period, the circuit determines that a proper cue has been received and distributes the same to the unit to be controlled. This type of cue detection is completely immune to variations in signal amplitude (which represents most of the noise on high fidelity tape decks) and represents a significant improvement in the signal-to-noise ratio of such system.

Another object of the invention is to provide a system having a highly regulated power supply which filters out any electronic noise .or line fluctuations which would cause false triggering of the audio-visual system. It is another object of this invention to provide circuits with solid state components either in discrete or integrated circuit form that will allow for light weight and reliable operation.

In accordance with the foregoing objects, there is provided a control unit which comprises means for encoding cues and placing them on the tape, means for decoding the cue signals to an input for each cue comparison circuit that indicates when a cue has been detected, an automatic gain, or level, control for eliminating the effects of spurious variations in the cue signals from the recorder and, finally, a cue coupling circuit which isolates the control unit from the audio-visual devices which are being controlled. These latter devices consume large amounts of electrical power and are notorious generators of noise. This can be from any of several sources such as motors, arcing and sparking contacts, solid state thyristors or controls on the intensity or speed of the audio-visual devices. If this noise is not isolated it can return to the control unit via ground loops formed by the connector wires running between the control unit and the devices being controlled and disrupt the decoding process.

In previous attempts to provide multi-media audiovisual presentation equipment, there has been suggested the use of various mechanical means of cue storage and detection such as punched tape systems or the like. Such systems have the disadvantage that if an error is made in the preparation of same or modification of the original presentation is desired, the overall presentation must be completely revised. In accordance with the invention there is provided a system wherein the programming of the presentation is on magnetic tape and therefore easily changed or erased at will. Further, the tapes for the presentation are readily duplicated for mass distribution.

. For a better understanding of the present invention, together with other and further objects and features thereof, reference is had to the following description taken in connection with the accompanying drawings, the scope of the invention being pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS Referring to the drawings:

FIG. 1 is a block diagram of a first embodiment of an audio-visual program presentation system constructed in accordance with the present invention;

FIG. 2 is a block diagram of a cue encoder used in the control unit of FIG. 1;

FIGS. 2a 2d depict pulse trains produced by the FIG. 2 encoder;

FIG. 3 is a block diagram of a cue decoder used in the control unit of FIG. 1;

FIGS. 3a 3e are waveforms depicting the pulse timing of the FIG. 3 decoder;

FIG. 4 is a circuit diagram of an AGC unit used in the FIG. 3 decoder;

FIG. 5 is a circuit diagram of a decommutator portion of the FIG. 3 decoder;

FIG. 6 is a circuit diagram of one of the cue comparison subsystems of the FIG. 3 decoder;

FIG. 6a is a circuit diagram of one of the cue couplers used in the FIG. 3 decoder;

FIG. 7 is a block diagram of a modified cue comparison subsystem which can be used in the FIG. 3 decoder;

FIG. 8 is a block diagram of a second embodiment of an audio-visual program presentation system constructed in accordance with the present invention;

FIG. 9 is a block diagram of one of the multiplex mixtures used in the FIG. 8 system;

FIG. 9a is a waveform of a signal developed by the FIG. 9 mixer;

FIG. 10 is a block diagram of one of the signal separators used in the FIG. 8 system;

FIGS. 10a and 10b are waveforms of signals developed by the FIG. 10 signal separator; and

FIG. 11 is a block diagram of a third embodiment of an audio-visual program presentation system constructed in accordance with the present invention.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS As shown in FIG. 1, the system includes an audiovisual control unit 10 and an ordinary home entertainment type two-channel tape recorder 12. First, second and third projectors 14, 16 and 18, respectively, an audio effects display 20 and a lighting effects display 22 are shown forming the auxiliary devices for an overall multi-media presentation.

The tape recorder 12 as contemplated by the invention may be a standard two-channel home entertainment stereo recorder but also may be any tape recorder having at least two or more channels for recording and playback of audio information. Such recorder includes the standard tape drive, pickup and recording heads and an audio input-output system. In the preferred embodiment, the recorder should have sound-with-sound capability. In other words, recorder 12 should preferably have the capability for playback on channel 1 while simultaneously recording on channel 2. The projectors 14, 16 and 18 may be standard slide projectors which are indexed to a new slide by a cue signal or may be dual slide projectors wherein the light is shifted from one prepared slide in place to another by a similar signal. One of the controlled projectors may be a movie projector if, during a certain sequence of the presentation, a short film clip is to be presented. The audio effects device 20 may be a tape recorder of the single channel or multi-channel type, a phonographic recorder player unit or any other similar audio device. Such an audio effect device might be used during the course of a lecture presentation for placing a background musical environment behind the speech being given. The lighting effects display 22 may merely be a spot light of variable colors, a continuously variable intensity light source, or an entire lighting system.

The control unit 10 is divided into two main sections, a cue encoder 24 and a cue decoder 26. The cue encoder 24 includes a keyboard 28 including a plurality of keys 29 individually having different ones of the channel designations A E marked thereon. The cue decoder 26 includes a multiplex quality indicator 30 and signal lights 31 and 32. The cue decoder 26 is shown connected to one of the playback channels of the stereo tape deck 12 after going through the function switch 33, while the cue encoder 24 is connected to the recording input of the same track on the stereo tape deck 12 and also to switch 33, which switch is depicted in FIG. 1 in a position for the purpose of recording cues on the previously mentioned recording input of the magnetic tape. In the recording position of switch 33, it will be noted that the cues from the cue encoder 24 are not only sent to the tape input but also directed to the cue decoder for the purpose of controlling the various display devices 14 through 22, respectively. During the course of preparation of the tape thus depicted, the system operates in the following manner. An audio presentation is first recorded on one of the channels of the stereo tape recorder. Track No. 2 thereof may be used for the receipt of the audio portion of the presentation through utilization of its standard audio input-output section 36. After preparation of this audio portion of the presentation on track No. 2 of stereo tape deck 12, the tape is then replayed with the audio-output on so that the operator may hear the audio presentation and track 1 is set to the record mode and all of the slide presentations and visual effects are turned on for viewing. During the course of the audio presentation, the operator will then push cue keys 29' mode of programming has proven to be far superior to any other known method and provides the operator with a large measure of personal satisfaction upon reviewing the results. When the cue signals for the auxiliary display units have thus been coded onto the first channel of the stereo tape for the entire presentation, the switch 33 may be set to its playback position (contact on right) and the tape rerun for verification of the operation of the auxiliary display units in proper synchronization with the audio program. Thus, the encoded signals present on the tape will be directed through the cue decoder for operation of the display devices. Obviously because of the use of magnetic tape, corrections or additions of cue information may be readily made. The cue decoder includes a signal quality protective monitoring system with outputs such as the signal level gauge 30 and signal lights 3l and 32 to indicate proper operation of the cue coding information from the magnetic tape. These monitor devices are very important when the audio-visual show must operate forextended periods as they give the operator warning of problems before they interrupt the show. These problems are, for example, tape and head wear and oxide build-up on the recorder playback mechanism.

FIGS. 2 and 2a-2d depict the details of the cue encoder 24 and the waveforms'provided thereby to control the operation of the display devices 14 to 22. The cue encoder 24 comprises a'master clock generator 40 and a series cascade connected group of delay circuits 42 to 50. Each of the encoder keys 29 are associated with respective delay circuits 42 50 respectively. The clock generator 40 is free running and designed to provide successive synchronization pulses which define a fixed and nonvariable frame interval of for example 20 ms. The cascaded delay circuits 42 50 duplicate the synchronization pulse delayed in time and, through adder-line 52, provide a train of cue pulses to the input amplifier of the stereo tape deck 12 and to switch 33. The train of pulses thus producedis depicted in FIGS. 2a 2d with the pulse output of each respective delay circuits designated A, B, C, D, and E. Each of the delay circuits 42 50 provides a fixed delay of, for example, l.5 ms. between each pulse when none of the encoder keys 29 are depressed. This would be a no-cue condition. FIG. 2a depicts the waveform when no-cue coding is provided to change the auxiliary .devices 14 to 22 accompanying the presentation. When a coding key 29 is depressed the time delay provided by the circuit is modified to either increase or decrease the delay of the pulse output therefrom. In the preferred embodiment of this invention, the effect of the key depression for keys 29 A-D is to decrease the pulse time delay to about one-half of the set delay, for example, 0.8 ms. This is effected by changing the time constant of the delay circuit. It should be'understood that separate channels can be provided by using both shorter and longer delays on the same pulse. Also, by providing proper width detection decoding, several trip points can be utilized in each direction. This would of course require several keys for each delay circuit, some for longer and some for shorter delays. Key 2%, which could be a dial, is connected to a variable resistance SI to provide continuous variations of the time delay of circuit 50. FIG. 2b depicts the waveform when the encoder key 29a has been depressed, FIG. 26 with key 29e depressed and FIG. 2d with keys 29a and 29a depressed. Thus, it will be seen that when no key is depressed the inverval between all of the pulses remain at a fixed interval, 1.5 ms. When the key 29a was depressed only the interval between the sync pulse S and the A-pulse was changed while when both the 29a and 29e keys were depressed the intervals between the S and A pulses and between the D and E pulses were changed. Thus, each channel is provided with pulse position modulation (PPM) with a decrease or increase in spacing between a given channel pulse and the preceding pulse being used to represent the cue information. Channels A to D are providedwith only finite encoding delay times while channel B may vary in analog manner for the purpose explained hereinafter. It should be noted that since the cue information is a shift of time and not amplitude of pulses or frequency of tones, that the PPM cue encoding provides distortion immunity against flutter and dropout.

Since the different channels are time multiplexed, the overall system can be described as being a multichannel time multiplexed pulse position modulation system. It is to be noted that during the operation of the system when a key isdepressed by an operator it will be depressed 'for some tenths of a second. Consequently, the corresponding channel pulse will be shifted for several successive frame intervals. This mode of cueing aids the system in overcoming the inherent distortion of the home entertainment stereo tape deck by requiring a certain number of successive frame intervals (each containing a PPM cue pulse change representing a cue) to occur before a cue is sent from the decoder to-any of the effects devices 14 22, for reasons to be described in more detail hereinafter.

The cue decoder unit 26 is depicted in FIG. 3 and comprises an automatic gain control (AGC) unit 54 which performs an amplitude discriminating and pulse shaping function.. The AGC unit 54 discriminates against signal amplitudes above and below a predetermined range. Signal values in the intermediate desired range that neglect both flutter and drop-out on the high end and tape hiss or noise on the low end are amplified to provide a train of pulses which assuming no tape flutter or drop-out from playback from the stereo tape deck will correspond to the train of coded pulses depicted for example in FIG. 3a.

The output train of pulses fromthe AGC unit 54 (FIG. 3a) is connected to a sync separator 55 and a level monitor 55a. Sync separator 55 has two output lines designated as X and Y. Sync separator 55 operates to separate out and to reproduce on the X output line only the recurring sync pulses S shown in FIG. 3a, with these separated sync pulses on line X being of positive polarity. The sync separator 55 operates to produce on the output line Y the complete train of pulses as represented in FIG. 3a with these pulses being of negative-going polarity. Sync separator output lines X and Y are connected to a decommutator formed by a series of cascade connected saturable switch circuits 56 64. Each of the saturable switch circuits 56 64 is bistable and includes a first input terminal N whereat a positive-going level change applied thereto will turn such circuit on. A second input terminal F is provided for each such circuit whereat a negative-going level change applied thereto will turn the circuit of Assuming initially that all of the saturable switch circuits 56 64 are in their of condition, then the next occuring sync pulse on line X serves to turn on the first saturable switch circuit 56. The next occurring pulse on line Y, namely, the channel A pulse, serves to turn the switch circuit 56 off again. This produces at the output of switch circuit 56 a width modulated negative-going pulse having a width corresponding to the time spacing between the S and A pulses which produced it. The positive-going trailing edge of the negative pulse at the output of switch circuit 56 serves to turn on the next saturable switch circuit 58. The next occuring pulse on line Y, namely, the channel B pulse, then serves to turn the second saturable switch 58 off. This produces at the output of the second saturable switch circuit 58 a negative-going width modulated pulse having a width corresponding to the time spacing between the A and B channel pulses which produced it. This sequential turning on and off of the saturable switch circuits progresses down the chain so that .there is produced at the output of the third saturable switch circuit 60 a negative-going width modulated pulse corresponding to the time spacing between the B and C pulses on line Y, at the output of the fourth saturable switch circuit 62 a negativegoing width modulated pulse corresponding to the time spacing between the C and D pulses on line Y and at the output of the fifth saturable switch circuit 64 a negative-going width modulated pulse corresponding to the time spacing between the'D and E pulses on Line Y. Thus, the separate cue channels (each corresponding to one of the variable delay networks 42 50 of the encoder 24) are divided out, each to'be processed separately.

The outputs of the saturable switch circuits 56 64 are individually connected to different ones of width reference one-shot multivibrator circuits 66 to 74 and add circuits 76 to 84 for separately discriminating the pulse widths of the width-modulated pulses for the different cue channels. Integrator circuits 86 to 94 and driver circuits 96 to 104 operate respective ones of cue coupling circuits 106 to 114 when the proper number of width-modulated pulses of the proper width appear at the outputs of the respective ones of the saturable switch circuits 56-64.

Each of the one-shots 66 to 74, when triggered on by the leading edge of the width-modulated pulse from its respective one of saturable switches 56-64, produces a positive-going pulse having a width (e.g., 1.5 milliseconds) correspondingto the nocue spacing between the pulses generated by encoder 24. If the encoder 24 provides for various widths of pulses, multiple sets of one-shot multivibrator and add circuits need to be provided. The output pulse of each saturable switch circuit 56-64 is compared with the output pulse of the corresponding one of one-shots 66 74, such comparison being performed by the corresponding one of add circuits 76 84. Waveforms representative of typical ones of these signals are depicted in FIGS. 3b 32. Assuming the PPM cue signals to be of the form of FIG. 2a (i.e., no cue), the output pulses from each of saturable switch circuits 56 64 will be of standard width, that is, l.5 milliseconds (no cue key depressed). Typical such no cue pulses from one of the saturable switches 56 64 are shown in FIG. 3b. Such negativegoing pulses cancel the positive-going reference pulses (FIG. 3c) from the corresponding one of the one shot circuits 66 74 producing no net signal at the output of the corresponding one of add circuits 76 84. Thus, no cue signal is supplied to the corresponding auxiliary device. When a channel has been coded by depressing a cue key, then the decoded negative pulses (FIG. 3d) from the corresponding saturable switch circuit are ap' proximately one-half of the width of the pulses (FIG. 3c) from the one-shot circuit and net positive pulses (FIG. 3e) appear at the input of the corresponding one of integrator circuits 86 94. Integrators 86 94 are designed to respond only to a positive input. Such an input produces an output signal which is sent to the corresponding one of couplers 106 114 to produce a change in the corresponding auxiliary device connected to the output thereof.

Integrators 86 94 provide an accumulator function which serves to eliminate the effects of spurious signals in the tape recorder output and removes the effects of signal dropout. The integrators 86 94 capacitatively store the signals received from the corresponding ones of add circuits 76 84 until a sufficient number, approximately five, have been received to trigger the driver amplifier circuits 96 104 to effect operation of the cue coupler circuits 106 1 14. Thus, a spurious signal frame will be insufficient to effect operationof the drivers, while compensation is made for signal loss for one or more frames since usually the encoder cue key will be depressed for several frames.

It should be noted that with the novel circuits of this invention working together to remove the effects of noise, flutter and dropout, the system has to experience quite a severe loss of signal for several frame intervals before any malfunction or miscues occur. The value of the level monitor 55a is apparent since when the signal deteriorates beyond a safe value at the output of the AGC, the level monitor switches off power supply circuit 55b which supplies operating voltage to the drivers 96 104 and no cues can be sent. This power supply voltage will stay off until the signal recovers or the level monitor is manually overridden by means of override circuit 550. Thus, the system isprotected from tape breakage or recorder malfunction.

The cue coupler circuits 106 114 may drive the auxiliary devices directly or, alternatively, may drive silicon controlled rectifier or triac switching circuits which, in turn, drive the auxiliary devices, thus providing a very wide versatility in the type of effect that can be controlled by the system. While the decoded add circuit pulses (FIG. 32) to the integrators 86 94 have been described as positive, it is obvious that polarities could be reversed to use negative pulses. Further, one or more of the encoder keying switches 29 and associated ones of delay circuits 42 50'could be constructed selectively to either increase or decrease the corresponding channel pulse delay, the use of increased delay producing negative-going pulses at the output of the corresponding one of add circuits 76 84.

An additional integrator circuit responsive only to negative-going pulses could then be connected to such add circuit to supply control signals to an additional driver and an additional cue coupler to provide an additional cue control channel. These changes would have the effect of-increasing the number of channels available without increased demands on the tape deck.

As noted, the cue decoder unit 26 depicted in FIG. 3 comprises an automatic gain control (AGC) unit 54 which performs an amplitude discriminating a pulse shaping function. A present preferred embodiment of AGC unit 54 is depicted in FIG. 4 and comprises a field effect transistor (FET) 116 and an inverting transistor 118. The input to the AGC unit 54 is to the gate electrode G of the field effect transistor 116 through a coupling capacitor 120 and resistance 122 connected between the gate electrode and ground. A network 124 is connected to the source electrode S of the field effect transistor 116 andis provided with a variable resistance for varying the sensitivity of the circuit. The output from the drain electrode D of the field effect transistor 116 is connected to the base of the inverting transistor 118 through a bias network 126. The collector electrode of the transistor, which is coupled to ground, forms the output of the circuit.

Transistors 116 and 118 are normally conductive. It is thus seen that the negative-going pulses obtained from tape recorder 12 and applied to the gate electrode of the field effect transistor 116 through capacitor 120 have the effect of turning said transistor off, provided said pulses have amplitudes in excess of a first predetermined value. The turning off of the field effect transistor 116 raises the voltage at the base of the inverting transistor 118 which reduces the bias available to the base emitter junction and turns said transistor off. When the transistor 118 turns off, its collector electrode returns toward a ground potential and saturates there as long as a pulse is present and the amplitude of such pulse is inexcess of a second and somewhat greater predetermined value. It is thus seen that both the minimum and maximum amplitude values of the cue pulses are controlled. Thus, as shown by FIG. 3a, the output of the AGC circuit is a negative-going PPM pulse train that has a controlled amplitude and clearly retains the width information needed for precise decoding. Since the output of the encoder is negative going and the output of the tape deck is negative going, the position of switch 33 has'no effect on the output of the AGC unit 54. The field effect transistor 116 is turned off only by a negative-going pulse of sufficiently high value to overcome the bias set by the RC network 124 and the positive portion of the pulse waveform increases the voltage on the gate of the field effect transistor 116 to turn it back on. The rise of the voltage at the base of transistor 118 caused by the turning off of the field effect transistor 116 turns off transistor 118. Transistor 118 remains off until such time as the field effect transistor 116 is turned back on, which event lowers the voltage to the base of the transistor 118 and turns the same back on. Because of the threshold bias provided by network 124 and the limiting action provided by the saturation of transistor 118, only signal values in an intermediate desired amplitude range provide the amplified output of the AGC unit 54. As long as the output from the tape recorder is greater than to percent of the recorded amplitude, perfect sets or frames of PPM cue pulses will be produced at the output of AGC unit 54. Should the signal input to the AGC drop below a safe operative point, the level monitor 55a disconnects the power to the drivers and warns the operator to clear upthe malfunction.

The saturable switch circuits 56 64 for the preferred embodiment of the invention are depicted schematically ingreater detail in FIG. 5 wherein it will be noted that each saturable switch circuit comprises a pair of complementary transistors, namely, a PNP transistor 126 and an NPNtransistor 128. The Y output from the sync separator unit 55 is applied to the emitters of each of the transistors 126 through blocking diodes 130. The synchronizing pulses on the X line of the sync separator unit 55 are applied to the saturable switch circuit 56 through a coupling capacitor 132. The greater majority of the time, transistors 126 and 128 will be non-conductive or turned off, this being one of the two bistable states of the switch circuit 56. Assuming this to be the case, a positive-going sync pulse through coupling capacitor 132 to the collector of transistor 126 and base of transistor 128 of switch circuit 56 biases these transistors to turn them on. The resulting current flow thereafter maintains transistors 126 and 128 in the on state, this being the second bistable state. In the condition state or on state, the voltage appearing at the circuit point intermediate the base of transistor 126 and the collector of transistor 128 and hence on output line 129 goes to substantially ground level and stays there for the entire duration of the time delay for channel A. The next occurring pulse on the Y output line of sync separator 55, namely, the negative-going channel A pulse is applied by way of coupling diode 130 to turn off transistor 126. This, in turn, turns off transistor 128. This causes the voltage on output line 129 to rise back up to the +V power supply level. Thus, it can now be seen that the output waveform (line 129) for the saturated switch circuit 56 is negative-going and has the exact same width as the original time spacing between the sync pulse S and the channel A pulse as set by the encoder 24 and its channel A key switch 29.

The positive-going trailing edgeof the output pulse of the first switch circuit 56 is supplied by way of coupling capacitor 131 to turn on the transistors 126 and 128 in the second switch circuit 58. The next occuring pulse on line'Y, namely, the channel B pulse, serves to turn the transistors in the second switch circuit 58 back off again. This produces on the output line 133 a negative-going pulse having a width equal to the time spacing between the channel A and channel B position modulated pulses. This process is thereafter repeated in sequence for the remaining switch circuits 60, 62 and 64.In this manner, the cue information for each channel is separated from the others and appears at the output of a single one of the switch circuits 56 64 for fur ther decoding.

Obviously, one saturable switch circuit is required for each position modulated cue pulse in the complete frame. However, each saturable switch circuit may drive more than one one-shot width detector thus having the effect of making available two or more cue channels for each frame pulse and saturable switch circuit used without increasing any demands made on the tape recorder 12.

Referring to FIG. 6, there is shown the details of a preferred form for the one-shot multivibrator 66 and the add circuit 76. The other one-shot and add circuit lll pairs may be of this same construction. As previously indicated, oneshot 66 and add circuit 76 provide a pulse width discrimination function for the width modulated pulses appearing at the output of the saturable switch 56. The one-shot multivibrator portion of FIG. 6 comprises a pair of cross-coupled transistors 134 and 136 with an RC timing network 138 being used to set the width of the positive-going reference pulses or comparison pulses (FIG. 3c) generated by such one-shot circuit. Such width is set equal to the no cue width of the pulses (FIG. 3b) appearing at the output of satu-' rable switch circuit 56. The output of saturable switch circuit 56 is connected to transistor 139 through resistor 140, transistor 139 being utilized only when there are several multivibrators connected to a single saturable switch circuit. If a single multivibrator is utilized for each saturable switch circuit, elements 139 and 140 may be deleted and the output of the saturable switch circuit connected directly to circuit point 137 of the one-shot. The leading edge of each negative-going pulse from the saturable switch circuit 56 triggers the multivibrator to generate a positive-going pulse which is applied to the upper end of diode 142 in add circuit 76. The negative-going pulse output of the saturable switch circuit is applied to the lower end of diode 144 in add circuit 76. There is produced on output line 145 of add circuit 76 a signal pulse corresponding in width to the lack of coincidence, if any, between the positivegoing one-shot reference pulse and the negative-going saturable switch pulse. If both pulses are of the same width, they completely offset one another and no net pulse appears on output line 145. If the saturable switch pulse is shorter, a net positive pulse appears on line 145 (see FIGS. 3c 32). If longer, a net negative pulse appears. Output line 145 is connected to the input of the integrator circuit 86 (FIG. 3). Each integrator and driver circuit is designed to respond only to either positive or negative pulses from the add circuit but not to both at the same time.

The coded pulse signals may be utilized for on-off switching or control action as mentioned above or may be used for continuous control as, for example, varying the intensity of a lighting effects display 22. Thus,in FIG. 2, the key 29B is disclosed as providing a continuously variable resistor or potentiometer for modifying the delay of delay circuit 50 in a continuous manner. Thus, the coded output from the Channel E saturable switch circuit 64 need not be merely a pulse of halfwidth as explained previously, but may be a pulse of any width. A circuit for fully utilizing such a pulse output is depicted in FIG. 7. As there shown, the Channel E width modulated pulse is compared with the output of the one-shot 74 in the add circuit 84. Since the coded signal is assumed to be a pulse of variable width, thus producing either a positive or negative output, the compared signal from add circuit 84 is directed to either a positive signal responding amplifier 150 or a negative signal responding amplifier 152. Power amplifiers 154 and 156 are provided to drive a servo motor 158 in either what may be considered the positive or negative direction. The servo motor 158 drives, for example, a rheostat 160 to control the lighting intensity of device 22 which is connected to terminal 161. The servo motor also drives a potentiometer which is a part of the RC time constant network (see FIG. 6) of the one-shot multivibrator 74 to adjust the width of the pulse output thereof. Thus, for example, if the output of the add circuit 84 is a positive net signal, the servo motor 158 is driven in the positive direction and the potentiometer of the one-shot multivibrator is adjusted to decrease the pulse width thereof until the output of the add circuit 84 is reduced to zero. At this time, the motor 158 stops and the width of the one shot pulse matches exactly with the time delay set by the operator of the cue encoder 24. Similarly, if the output of the add circuit 84 is such that the'coded signal has produced a negative output at the output of add circuit 84, the servo motor 158 will be driven in the negative direction while simultaneously adjusting one shot 74 to increase its pulse width until a zero add circuit output signal is developed, whereupon the motor 158 stops. In this manner, the width of the coded pulse can be utilized to provide continuous analog control of any output device. This could be used to control the intensity of lights or the speed of a motor or the volume of sound from a sound source.

The cue coupling device 106 of FIG. 3 is shown in greater detail in FIG. 6a. The other cue couplers 108 114 are of this same construction. As shown in FIG. 6a, a light bulb 146 shines on a light dependent or photosensitive element 147 which may be a light dependent resistor such as, for example, a cadmium sulfide cell or a PN junction diode, light bulb 146 and element 147 being contained in alight-tight box (not shown). Since only light radiation connects the input bulb I46 and an output switching device 148, which might be an SCR, as shown, or a triac or an electromechanical relay, the cue encoding system will be completely electrically isolated from the operation of the auxiliary device connected across output terminals 149. Preferably, each cue coupler should be located with its projector or other auxiliary device and the driving lines running from the control unit 10 to the cue couplers 106 114 should be of low impedance. When this is done, the control unit l0v is very effectively insulated from' any ground loops and disruptive circuit current surges.

If it is desired to record audio program material on both channels of the stereo tape, the system may be made frequency responsive and utilize the coded PPM signal superimposed over one or both of the channels. A system of this type is shown to FIG. 8 and would allow full stereo sound and independent control of a plurality of auxiliary devices with completely silent cues utilizing an ordinary home entertainment type stereo tape recorder. Two stereo tape recorders 12a and 12b are illustrated together with two cue encoders 24a and 24b and two cue decoders 26a and 26b. All of these components are similar to those previously explained with respect to the system of FIG. 1. Interposed between the cue encoders 24a and 24b and the channels of these stereo tape decks 12a and 12b are multiplex mixers 162a and 162b. Signal separators 164a and l64lb are interposed between the channels of the tape deck 12b and cue decoders 26a and 26b.

The multiplex mixer 162a is shown in more detail in FIG. 9. The second mixer l62b is of this same construction. Mixer 162a includes a high frequency audio oscillator 166 which produces a high frequency audio tone signal in, for example, the 10 to 15 kilohertz range. This high frequency audio tone is fed to a gate 168 which is controlled by the PPM cue pulses from the cue encoder 24a to produce at the output of gate 168 bursts of high frequency oscillation corresponding to the pulses produced by the cue encoder 24a. The cue information is now represented by the time spacing between the bursts of high frequency energy, a portion of the output of gate 168 being represented by the waveform of FIG. 9a. The time between bursts is the same as the time between the pulses shown'in FIG. 2a. The audio program signal from one channel (Track 2) of the stereo tape deck 12a is fed through a notch filter 170 which passes all frequencies except for a very narrow band of frequencies centered at the frequency of oscillation of the high frequency oscillator 166. Because of the narrowness of the stop band of the notch filter, the audio program signal will remain essentially unaffected even though a narrow band of frequencies has been removed from such audio program signal. The pulses of high frequency oscillations from the gating circuit 168 and the audio program signal from the notch filter 170 are fed to a mixer circuit 172 which superimposes the high frequency tone bursts onto the audio signal. The resulting composite signal appearing at the output of mixer 172 is directed to the tape receorder 12b for recording on one track of the magnetic tape contained therein.

It should be noted that a primary object of this type of frequency multiplexing is to keep the cueing signals from being heard by the listening audience during the subsequent presentation of the audio program material. Therefore, while the audio program material is mixed through mixer 172. at a high level, the tone bursts are mixed through at a much lower level, of, for example, to decibels below the level of the program material. It should also be clear that it is desirable to remove with notch filter 170 all frequency components from the audio program that might be mistaken as a cue signal by the signal separator 164a. This latter feature precludes any stray energy from the much larger audio program signal from causing false triggering of a high gain tuned amplifier 178 located in signal separator 164a and to be considered hereinafter.

In the operation of the system of FIG. 8 it is assumed that the desired stereo program material is first 'recorded by the first stereo tape deck 12a. Uponplayback of the-tape by tape deck 12a, an 'operatormay encode one or more channels with cue information by operation of the cue keys of cue encoders 24a and 24b, which information is recorded on the channels of the second stereo tape deck 12b along with the stereo pro gram material. If a stereo tape deck of the type having a simultaneous playback and recording capability is used, the audio inputs and outputs of the frequency encoders 162a and 162b maybe directly connected therewith and the use of a second stereo tape deck is unnecessary.

Simultaneously with the encoding of the audio and cue signals on both channels of the magnetic tape in recorder 12b, cueing signals are stripped from the two composite signals by signal separators 164a and 164b. Both of these signal separators 164a and 164k are of the same construction, the former being shown in greater detail in FIG. 10. As there seen, signal separator 164a comprises a high boost filter 174 which attenuates the lower frequency portion of the audio spectrum relative to the higher frequency portion of the audio spectrum, the latter including the cue signal tone frequency. This modified signal is amplified by an amplifier 176 and supplied to a tuned amplifier circuit 178 and a notch filter 180. The notch filter 180 passes all audio frequencies except for a very narrow band of frequencies centered at the cue signal tone frequency. The filtered signal is supplied to a low boost filter 182 which attentuates the higher frequency portion of the audio spectrum relative to the lower frequency portion of the audio spectrum in a manner which is the exact converse of the attentuating action in the earlier highboost filter 174. The net overall effect of the high-boost filter 174 and the low-boost filter 182 is to provide an essentially flat passband from the input of the former to the output of the latter excepting, of course, the frequencies in the stop band of notch filter 180. The resulting audio program signal at the output of low-boost filter 182 is supplied to an appropriate amplifier and loudspeaker system (not shown) for presentation to a listening audience. Because of the tone signal loss in notch filter (20 to 25 decibles) and the original low level of the tone bursts, the cue information is not heard by the listening audience.

The tuned amplifier 178 is sharply tuned to the frequency of the high frequency audio oscillator 166, i.e., the cue signal tone frequency, and has a very high gain for amplifying'thecue signal bursts which are then supplied'to a saturable driver circuit 184 which converts the high frequencytone bursts into a rectangular wave output of the type originally appearing at the output of the cue encoder 24a. Each time the tuned amplifier 178 produces at its output a high frequency tone burst (FIG. 10a), the normally off]saturate d driver circuit 184 turns on for the duration of the burst, thus producing a waveofrm as shown in FIG. 10b. These detected cue signals are inverted by an output stage in the driver circuit 184 to produce negative-going pulses which are then supplied to and decommutated by the cue decoder circuit 26a in the manner explained perviously.

While the foregoing system of FIG. 8 has been illustrated as encoding and decoding different one information on both channels or both tracks of the magnetic tape, it will be understood that, if desired, only a single encoder could be used to encode cue signals on only one of the tape channels. 'As a further alternative, the same 'cue information could be encoded on both tape channels for checking oneagainst the other for minimizing the effect of tape dropout on playback.

The stereo system of FIG. 8 may be converted into a monaural system by simply cutting the FIG. 8 system in half. In other words, monaural tape recorders would be used in place of the stei'eo tape decks 12a and 12b and only one set of the remaining components, for example, cue encoder 24a, multiplex mixer 162a, signal separator 164a and cue decoder 26a, would be used in connection therewith. The operation would be the same as described above and would allow a monaural tape unit to provide a completely automatic audiovisual program presentation.

Referring to FIG. 11, there is shown a modified form of monaural system having a pair of monaural tape recorders 186a and 18612. A multiplex mixer 162C is provided with a keying switch 188 for actuating the gating circuit thereof. In other words, mixer 1620 is of the same construction as shown in FIG. 9 with the keying switch 188 being connected to the gate 168 in place of r the cue encoder 24a. Closing of switch 188 causes gate 168 to produce a tone burst at the output thereof. Upon playback of the previously recorded audio program material by the monaural tape recorder 186a, tone burst cueing pulses are mixed with the program signal at the appropriate points by a momentary closing of switch 188 and the resulting composite signal is supplied to the second monaural tape recorder l86b for recording on the tape therein. The signal separator 164e, which may be of the same construction as that shown in FIG. 10, utilizes the high frequency cue pulses to drive an output switch circuit 190 for an auxiliary device by 'directing each separator output pulse through a direct-current amplifier circuit 192 which converts same into a power pulse for driving the output switch 190. The FIG. 11 system is a simplified monaural system for use with a single slide projector or other auxiliary device, the advancement mechanism or com trol mechanism in such projector or other device being connected to the output of the output switch 190 by way of an appropriate connector cable.

While the tone frequency produced by the highfrequency audio oscillator 166 in the multiplex mixers has been disclosed as being near the upper end of the human audible range, it may in some cases be necessary to utilize a lower tone frequency, particularly if the tape recorders contemplated to be used are not of sufficient fidelity to handle frequencies in the higher range.

While there have been described what are at present considered to be preferred embodiments of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore intended to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. An audio-visual display system comprising:

magnetic tape recorder means for recording audio program signals on magnetic tape and for reproducing same during playback of a recorded tape;

a plurality of auxiliary display units for producing audio effects or visual effects or both;

cue encoding means coupled to the tape recorder means for recording plural channel cue signals on the magnetic tape at desired points in the audio program, said cue encoding means including means for producing time-multiplexed signals which .comprise repetitive groups of pulses and means for independently changing the time interval between each of a plurality of selected pulses and a corresponding adjacent pulse in each group to thereby provide a plurality of independnet control channel cue signals for control channels designated by the selected pulses;

and cue decoding means coupled to the tape recorder means and to the auxiliary display units during tape playback and responsive to reproduced control channel cue signals for automatically and independently controlling the different auxiliary display units in step with the playback of the recorded audio program signals.

2. An audio-visual display system in accordance with claim 1 wherein the cue encoding means includes:

a clock pulse generator;

a series of cascaded delay circuits, the first of which is coupled to the clock pulse generator;

means for adding the output signals from the clock pulse generator and the delay circuits to produce a train of cue pulses;

and means for independently changing the time delay of each delay circuit for providing a plurality of independent control channel cue signals. 3. An aduio-visual.display system in accordance with claim 2 wherein the time delay changing means for at least one of the delay circuits comprises an analog device for varying the time delay in a continuous manner. 4. An audio-visual display system in accordance with claim 1 wherein the system further includes:

multiplex mixer means coupled between the cue encoding means and the tape recorder means for converting the control channel cue signals to tone burst signals and combining same with at least some of the audio program signals for enabling the combined signals to be recorded on a common track on the magnetic tape; and frequency selective signal separator means coupled between the tape recorder means and the cue decoding means during tape playback for separating the cue signal tone bursts from the intermingled audio program signals and for converting same to pulse type signals for use by the cue decoding means. 5. An audio-visual display system in accordance with claim 4 wherein:

the multiplex mixer means is constructed so that the level of the recorded cue signal tone bursts is substantially less than the average level of the recorded audio program signals with which it is combined;

and the signal separator means includes frequency selective means for boosting the level of the cue signal tone bursts relative to the level of the lower frequency components of the intermingled audio program signals before the cue signal tone bursts are separated from the audio program signals.

6. An audio-visual display system in accordance with claim 4 wherein the multiplex mixer means comprises:

an audio-frequency oscillator;

gate circuit means coupled to the output of the oscillator and responsive to the control channel cue signals produced by the cueencoding means for producing at the output of such gate circuit means tone burst signals corresponding in position and duration to the pulses of the control channel cue signal;

and circuit means for mixing the tone burst signals with an audio program signal.

7. An audio-visual display system in accordance with claim 4 wherein the signal separator means comprises:

high-boost filter circuit means for boosting the level of the cue signal tone bursts relative to the level of the lower frequency components of the intermingled audio program signals;

sharply tuned bandpass circuit means coupled to the high-boost filter circuit means for passing substantially only the cue signal tone bursts;

circuit means coupled to the output of the bandpass circuit means for converting the tone bursts to pulse type signals and for supplying same to the cue decoding means;

and low-boost filter circuit means for boosting the level of the lower frequency components of the audio program signals relative to the higher frequency components, such circuit means being constructed so that the low frequency boost equalizes the low frequency attenuation experienced in the high-boost filter circuit means to develop an audio output signal for use by a loudspeaker type reproduction system.

8. An audio-visual display system in accordance with claim 7 wherein the multiplex mixer means comprises:

an audio-frequency oscillator;

gate circuit means coupled to the output of the oscillator and responsive to the control channel cue signals produced by the cue encoding means for producing at the output of such gate circuit means tone burst signals corresponding in position and duration to the pulses of the control channel cue signals;

and circuit means for mixing the tone burst signals with an audio program signal to provide the combined signals for the magnetic. tape recorder means.

9. An audio-visual display system in accordance with claim 1 wherein one pulse in each group is a sync pulse and the other are position-modulated cue pulses for different control channels and wherein the cue decoding means comprises:

automatic gain control circuit means for receiving and conditioning the cue pulses;

sync separator means responsive to the sync pulse in each group for producing separate sync signals;

saturable switch circuit means responsive to the cue pulses and the separate sync signals for producing separate sets of width modulated pulses on a plurality of output lines, the pulses on any given output line being width modulated in accordance with the position modulation of the pulses for a particular one of the control channels;

a plurality of width detector circuit means individually coupled to different ones of the saturable switch circuit output lines for producing separate control signals for the different control channels;

and a plurality of signal coupling means for individually coupling-the width detector circuit means to different ones of the auxiliary display units.

10. An audio-visual display system in accordance with claim 9 wherein the cue encoding means comprises: I

a clock pulse generator; I

a series of cascaded delay circuits, the first of which is coupled to the clock pulse generator;

means for adding the output signals from the clock pulse generator and delay circuits to produce a train of cue pulses;

and means for independently changing the time delay of each delay circuit for providing a plurality of independent control channel cue signals.

ll. An audio-visual display system in accordance with claim 9 wherein the cue pulses received by the automatic gain control circuit means are negative-going pulses and such automatic gain control circuit means comprises:

a field effect transistor having gate, source and drain electrodes;

circuit means for biasing the field effect transistor to a normally conductive condition; I

circuit means for enabling the gate electrode of the field effect transistor to receive the incoming negative-going cue pulses;

a p-n-p transistor having bare, emitter and collector electrodes;

circuit means for coupling the base electrode of the p-n-p transistor to the drain electrode of the field effect transistor and for biasing the p-n-p transistor to a normally conductive condition;

and output circuit means coupled to the collector electrode of the p-n-p transistor for providing negative-going amplitude discriminated and conditioned cue pulses.

12. An audio-visual display system in accordance with claim 9 wherein the saturable switch circuit means comprises:

a series of cascaded switch circuits each comprising n-p-n transistor, circuit means for applying operating voltage between the emitter and collector electrodes of the n-p-n transistor, a p-n-p transistor having its collector electrode connected to the base electrode of the n-p-n transistor and having its base electrode connected to the collector electrode of the n-p-n transistor and circuit means for biasing both transistor to a normally non-conductive condition;

circuit means for supplying the separate sync signals to the base electrode of the n-p-n transistor in the first switch circuit in the series for repetitively turning such first switch circuit on;

circuit means for coupling the n-p-n collector electrode of each switch circuit to the n-p-n base electrode of the next switch circuit in the series for turning the latter switch circuit on when the earlier switch circuit turns off;

circuit means for supplying the cue pulses to the p-n-p emitter electrodes of all of the switch circuits for turning off the switch circuit which is turned on when a cue pulse occurs;

and the output lines for the saturable switch circuit means being individually coupled to the n-p-n collector electrodes in different ones of the switch circuits.

13. An audio-visual display system in accordance with claim 9 wherein each width detector circuit means includes:

one-shot multivibrator circuit means coupled to one of the saturable switch circuit output lines and responsive to the leading edge of each width modulated pulse appearing on such output line for producing a reference pulse of predetermined width;

add circuit means responsive to each width modulated pulse and to the one-shot reference pulse produced by the leading edge thereof for producing an output pulse having a width corresponding to the difference in widths of the width modulated pulse and the reference pulse;

and integrator circuit means for integrating the add circuit output pulses for producing a control signal for the particular control channel with which the width detector circuit means is associated.

14. An audio-visual display system in accordance with claim 9 wherein each signal coupling means includes:

light emitting means coupled to the output of one of the width detector circuit means for emitting light in response to the appearance of a control signal at such output;

light responsive means responsive to light emitted by the light emitting means for producing a control effect;

and circuit means coupled to the light responsive means and to one of the auxiliary display units and responsive to the control effect produced by the light responsive means for controlling the auxiliary display unit in accordance therewith.

15. An audio-visual display system in accordance with claim 9 wherein: Y

the cue encoding means includes a clock pulse generator; a series of cascaded delay circuits the first of which is coupled to the clock pulse generator, means for adding the output signals from the clock pulse generator and the delay circuits to produce a train of cue pulses, and means for independently changing the time delay of each delay circuit for providing a plurality of independent control channel cue signals, the time delay changing means for at least one of the delay circuits comprising an analog device for varying the time delay in a continuous manner;

and the width detector circuit means and signal coupling means for the control channel employing the analog device includes one-shot multivibrator circuit means responsive to the leading edge of each width modulated pulse for the analog control channel for producing a comparison pulse, comparing circuit means for comparing the width modulated pulses with the comparison pulses for producing an error signal, a servo mechanism controlled by the error signal for enabling a continuous adjustment of the auxiliary display unit controlled by the analog control channel, and means coupled to the servo mechanism for adjusting the pulse width of the one-shot comparison pulses until a practically zero error signal is produced by the comparing circuit means.

16. An audio-visual display system comprising:

magnetic tape recorder means for reproducing audio program signals and plural channel cue signals recorded on a magnetic tape wherein the recorded cue signals are in the form of repetitive groups of time-multiplexed pulses wherein one pulse in each group is a sync pulse; and the others are positionmodulated pulses for different control channels;

a plurality of auxiliary display units for producing audio effects or visual effects or both;

automatic gain control circuit means coupled to the tape recorder means during tape playback for receiving and conditioning the cue signal pulses;

sync separator means responsive to the sync pulse in each group for producing separate sync signals;

saturable switch circuit means responsive to the one signal pulses and the separate sync signals for producing separate sets of width modulated pulses on a plurality of output lines, the pulses on any given output line being width modulated in accordance with the position modulation of the pulses for a particular one of the control channels;

a plurality of width detector circuit means individually coupled to different ones of the saturable switch circuit output lines for producing separate control signals for the different control channels;

and a plurality of signal coupling means for individually coupling the width detector circuit means to different ones of the auxiliary display units for automatically and independently controlling the different auxiliary display units in step with the playback of the recorded audio program signals.

17. An audio-visual display system comprising:

magnetic tape recorder means for recording audio signals on magnetic tape and for reproducing same during playback of a recorded tape;

an auxiliary display unit for producing audio or visual effects;

means for producing cue signals in the form of audiofrequency tone bursts in which the frequency of the oscillations in each tone burst is greater than a predetermined frequency;

signal combining means for combining such tone bursts with an audio program signal and supplying the combined signals to the magnetic tape recorder means for recording same on a common tract on a magnetic tape; first frequency selective circuitmeans coupled to the magnetic tape recorder means during tape playback for separating the cue signal tone bursts from the audio program signal; said circuit means including high-boost filter circuit means for boosting the level of signal components at frequencies greater than the predetermined frequency relative to the level of signal components at frequencies less than the predetermined frequency and sharply tuned bandpass circuit means coupled to the output of the high-boost filter circuit means for passing substantially only the cue signal tone bursts;

means responsive to the separated cue signal tone bursts for automatically controlling the auxiliary display unit in step with the playback of the recorded audio program signal;

and second frequency selective circuit means coupled to the magnetic tape recorder means during tape playback for separating the audio program signal from the cue signal tone bursts for providing an uncontaminated audio program signal for use by a loudspeaker type sound reproduction system, said second circuit means including low-boost filter circuit means coupled to the output of the high-boost filter circuit means for boosting the level of signal components at frequencies less than the predetermined frequency relative to the level of signal components at frequencies greater than the predetermined frequency, such low-boost filter circuit means being constructed so that the low frequency boost equalizes the low frequency attenuation provided by the high-boost filter circuit means.

18. An audio-visual display system in accordance with claim 17 wherein the signal combining means includes notch filter circuit means sharply tuned to the frequency of the tone burst oscillations for minimizing tone burst frequency components in the audio program signal before it is combined with the cue signal tone bursts.

19. An audio-visual display system in accordance with calim 17 wherein the second frequencey selective circuit means includes notch filter circuit means sharply tuned to the tone burst oscillation frequency for minimizing tone burst frequency components in the audio program signal to be supplied to the sound reproduction system.

20. An audio-visual display system in accordance with claim 17 wherein:

the first frequency selective circuit means includes notch filter circuit means sharply tuned to the tone burst oscillation frequency for minimizing tone burst frequency components in the audio program signal before it is combined with the cue signal tone bursts;

and the second frequency selective circuit means includes notch filter circuit means sharply tuned to the tone burst oscillation frequency for minimizing tone burst frequency components in the audio program signal to be supplied to the sound reproduction system.

21. An audio-visual display system comprising:

magnetic tape recorder means for recording audio program signals on magnetic tape and for reproducing same during playback of a recorded tape;

at least one auxiliary display unit for producing audio effects or visual effects or both; and

cue encoding means coupled to the tape recorder means for recording channel cue signals on the magnetic tape at desired points in the audio program, said cue encoding means including means for producing signals which comprise repetitive groups of at least two pulses and means for independently changing the time interval between a selected pulse and a corresponding adjacent pulse in each group to thereby provide a control channel cue signal for a control channel designated by the selected pulse further including cue decoding means coupled to the tape recorder means and to the auxiliary display unit during tape playback and responsive to a reproduced control channel cue signal for automatically controlling the auxiliary display unit in step with the playback of the recorded audio program signals. 

1. An audio-visual display system comprising: magnetic tape recorder means for recording audio program signals on magnetic tape and for reproducing same during playback of a recorded tape; a plurality of auxiliary display units for producing audio effects or visual effects or both; cue encoding means coupled to the tape recorder means for recording plural channel cue signals on the magnetic tape at desired points in the audio program, said cue encoding means including means for producing time-multiplexed signals which comprise repetitive groups of pulses and means for independently changing the time interval between each of a plurality of selected pulses and a corresponding adjacent pulse in each group to thereby provide a plurality of independnet control channel cue signals for control channels designated by the selected pulses; and cue decoding means coupled to the tape recorder means and to the auxiliary display units during tape playback and responsive to reproduced control channel cue signals for automatically and independently controlling the different auxiliary display units in step with the playback of the recorded audio program signals.
 2. An audio-visual display system in accordance with claim 1 wherein the cue encoding means includes: a clock pulse generator; a series of cascaded delay circuits, the first of which is coupled to the clock pulse generator; means for adding the output signals from the clock pulse generator and the delay circuits to produce a train of cue pulses; and means for independently changing the time delay of each delay circuit for providing a plurality of independent control channel cue signals.
 3. An aduio-visual display system in accordance with claim 2 wherein the time delay changing means for at least one of the delay circuits comprises an analog device for varying the time delay in a continuous manner.
 4. An audio-visual display system in accordance with claim 1 wherein the system further includes: multiplex mixer means coupled between the cue encoding means and the tape recorder means for converting the control channel cue signals to tone burst signals and combining same with at least some of the audio program signals for enabling the combined signals to be recorded on a common track on the magnetic tape; and frequency selective signal separator means coupled between the tape recorder means and the cue decoding means during tape playback for separating the cue signal tone bursts from the intermiNgled audio program signals and for converting same to pulse type signals for use by the cue decoding means.
 5. An audio-visual display system in accordance with claim 4 wherein: the multiplex mixer means is constructed so that the level of the recorded cue signal tone bursts is substantially less than the average level of the recorded audio program signals with which it is combined; and the signal separator means includes frequency selective means for boosting the level of the cue signal tone bursts relative to the level of the lower frequency components of the intermingled audio program signals before the cue signal tone bursts are separated from the audio program signals.
 6. An audio-visual display system in accordance with claim 4 wherein the multiplex mixer means comprises: an audio-frequency oscillator; gate circuit means coupled to the output of the oscillator and responsive to the control channel cue signals produced by the cue encoding means for producing at the output of such gate circuit means tone burst signals corresponding in position and duration to the pulses of the control channel cue signal; and circuit means for mixing the tone burst signals with an audio program signal.
 7. An audio-visual display system in accordance with claim 4 wherein the signal separator means comprises: high-boost filter circuit means for boosting the level of the cue signal tone bursts relative to the level of the lower frequency components of the intermingled audio program signals; sharply tuned bandpass circuit means coupled to the high-boost filter circuit means for passing substantially only the cue signal tone bursts; circuit means coupled to the output of the bandpass circuit means for converting the tone bursts to pulse type signals and for supplying same to the cue decoding means; and low-boost filter circuit means for boosting the level of the lower frequency components of the audio program signals relative to the higher frequency components, such circuit means being constructed so that the low frequency boost equalizes the low frequency attenuation experienced in the high-boost filter circuit means to develop an audio output signal for use by a loudspeaker type reproduction system.
 8. An audio-visual display system in accordance with claim 7 wherein the multiplex mixer means comprises: an audio-frequency oscillator; gate circuit means coupled to the output of the oscillator and responsive to the control channel cue signals produced by the cue encoding means for producing at the output of such gate circuit means tone burst signals corresponding in position and duration to the pulses of the control channel cue signals; and circuit means for mixing the tone burst signals with an audio program signal to provide the combined signals for the magnetic tape recorder means.
 9. An audio-visual display system in accordance with claim 1 wherein one pulse in each group is a sync pulse and the other are position-modulated cue pulses for different control channels and wherein the cue decoding means comprises: automatic gain control circuit means for receiving and conditioning the cue pulses; sync separator means responsive to the sync pulse in each group for producing separate sync signals; saturable switch circuit means responsive to the cue pulses and the separate sync signals for producing separate sets of width modulated pulses on a plurality of output lines, the pulses on any given output line being width modulated in accordance with the position modulation of the pulses for a particular one of the control channels; a plurality of width detector circuit means individually coupled to different ones of the saturable switch circuit output lines for producing separate control signals for the different control channels; and a plurality of signal coupling means for individually coupling the width detector circuit means to different ones of the auxiliary display units.
 10. AN audio-visual display system in accordance with claim 9 wherein the cue encoding means comprises: a clock pulse generator; a series of cascaded delay circuits, the first of which is coupled to the clock pulse generator; means for adding the output signals from the clock pulse generator and delay circuits to produce a train of cue pulses; and means for independently changing the time delay of each delay circuit for providing a plurality of independent control channel cue signals.
 11. An audio-visual display system in accordance with claim 9 wherein the cue pulses received by the automatic gain control circuit means are negative-going pulses and such automatic gain control circuit means comprises: a field effect transistor having gate, source and drain electrodes; circuit means for biasing the field effect transistor to a normally conductive condition; circuit means for enabling the gate electrode of the field effect transistor to receive the incoming negative-going cue pulses; a p-n-p transistor having bare, emitter and collector electrodes; circuit means for coupling the base electrode of the p-n-p transistor to the drain electrode of the field effect transistor and for biasing the p-n-p transistor to a normally conductive condition; and output circuit means coupled to the collector electrode of the p-n-p transistor for providing negative-going amplitude discriminated and conditioned cue pulses.
 12. An audio-visual display system in accordance with claim 9 wherein the saturable switch circuit means comprises: a series of cascaded switch circuits each comprising n-p-n transistor, circuit means for applying operating voltage between the emitter and collector electrodes of the n-p-n transistor, a p-n-p transistor having its collector electrode connected to the base electrode of the n-p-n transistor and having its base electrode connected to the collector electrode of the n-p-n transistor and circuit means for biasing both transistor to a normally non-conductive condition; circuit means for supplying the separate sync signals to the base electrode of the n-p-n transistor in the first switch circuit in the series for repetitively turning such first switch circuit on; circuit means for coupling the n-p-n collector electrode of each switch circuit to the n-p-n base electrode of the next switch circuit in the series for turning the latter switch circuit on when the earlier switch circuit turns off; circuit means for supplying the cue pulses to the p-n-p emitter electrodes of all of the switch circuits for turning off the switch circuit which is turned on when a cue pulse occurs; and the output lines for the saturable switch circuit means being individually coupled to the n-p-n collector electrodes in different ones of the switch circuits.
 13. An audio-visual display system in accordance with claim 9 wherein each width detector circuit means includes: one-shot multivibrator circuit means coupled to one of the saturable switch circuit output lines and responsive to the leading edge of each width modulated pulse appearing on such output line for producing a reference pulse of predetermined width; add circuit means responsive to each width modulated pulse and to the one-shot reference pulse produced by the leading edge thereof for producing an output pulse having a width corresponding to the difference in widths of the width modulated pulse and the reference pulse; and integrator circuit means for integrating the add circuit output pulses for producing a control signal for the particular control channel with which the width detector circuit means is associated.
 14. An audio-visual display system in accordance with claim 9 wherein each signal coupling means includes: light emitting means coupled to the output of one of the width detector circuit means for emitting light in response to the appearance of a control signal at such output; light responsive means responsive to light emitteD by the light emitting means for producing a control effect; and circuit means coupled to the light responsive means and to one of the auxiliary display units and responsive to the control effect produced by the light responsive means for controlling the auxiliary display unit in accordance therewith.
 15. An audio-visual display system in accordance with claim 9 wherein: the cue encoding means includes a clock pulse generator; a series of cascaded delay circuits the first of which is coupled to the clock pulse generator, means for adding the output signals from the clock pulse generator and the delay circuits to produce a train of cue pulses, and means for independently changing the time delay of each delay circuit for providing a plurality of independent control channel cue signals, the time delay changing means for at least one of the delay circuits comprising an analog device for varying the time delay in a continuous manner; and the width detector circuit means and signal coupling means for the control channel employing the analog device includes one-shot multivibrator circuit means responsive to the leading edge of each width modulated pulse for the analog control channel for producing a comparison pulse, comparing circuit means for comparing the width modulated pulses with the comparison pulses for producing an error signal, a servo mechanism controlled by the error signal for enabling a continuous adjustment of the auxiliary display unit controlled by the analog control channel, and means coupled to the servo mechanism for adjusting the pulse width of the one-shot comparison pulses until a practically zero error signal is produced by the comparing circuit means.
 16. An audio-visual display system comprising: magnetic tape recorder means for reproducing audio program signals and plural channel cue signals recorded on a magnetic tape wherein the recorded cue signals are in the form of repetitive groups of time-multiplexed pulses wherein one pulse in each group is a sync pulse; and the others are position-modulated pulses for different control channels; a plurality of auxiliary display units for producing audio effects or visual effects or both; automatic gain control circuit means coupled to the tape recorder means during tape playback for receiving and conditioning the cue signal pulses; sync separator means responsive to the sync pulse in each group for producing separate sync signals; saturable switch circuit means responsive to the cue signal pulses and the separate sync signals for producing separate sets of width modulated pulses on a plurality of output lines, the pulses on any given output line being width modulated in accordance with the position modulation of the pulses for a particular one of the control channels; a plurality of width detector circuit means individually coupled to different ones of the saturable switch circuit output lines for producing separate control signals for the different control channels; and a plurality of signal coupling means for individually coupling the width detector circuit means to different ones of the auxiliary display units for automatically and independently controlling the different auxiliary display units in step with the playback of the recorded audio program signals.
 17. An audio-visual display system comprising: magnetic tape recorder means for recording audio signals on magnetic tape and for reproducing same during playback of a recorded tape; an auxiliary display unit for producing audio or visual effects; means for producing cue signals in the form of audio-frequency tone bursts in which the frequency of the oscillations in each tone burst is greater than a predetermined frequency; signal combining means for combining such tone bursts with an audio program signal and supplying the combined signals to the magnetic tape recorder means for recording same on a common tract on a magnetic tape; first frequency selective circuit means couPled to the magnetic tape recorder means during tape playback for separating the cue signal tone bursts from the audio program signal; said circuit means including high-boost filter circuit means for boosting the level of signal components at frequencies greater than the predetermined frequency relative to the level of signal components at frequencies less than the predetermined frequency and sharply tuned bandpass circuit means coupled to the output of the high-boost filter circuit means for passing substantially only the cue signal tone bursts; means responsive to the separated cue signal tone bursts for automatically controlling the auxiliary display unit in step with the playback of the recorded audio program signal; and second frequency selective circuit means coupled to the magnetic tape recorder means during tape playback for separating the audio program signal from the cue signal tone bursts for providing an uncontaminated audio program signal for use by a loudspeaker type sound reproduction system, said second circuit means including low-boost filter circuit means coupled to the output of the high-boost filter circuit means for boosting the level of signal components at frequencies less than the predetermined frequency relative to the level of signal components at frequencies greater than the predetermined frequency, such low-boost filter circuit means being constructed so that the low frequency boost equalizes the low frequency attenuation provided by the high-boost filter circuit means.
 18. An audio-visual display system in accordance with claim 17 wherein the signal combining means includes notch filter circuit means sharply tuned to the frequency of the tone burst oscillations for minimizing tone burst frequency components in the audio program signal before it is combined with the cue signal tone bursts.
 19. An audio-visual display system in accordance with calim 17 wherein the second frequencey selective circuit means includes notch filter circuit means sharply tuned to the tone burst oscillation frequency for minimizing tone burst frequency components in the audio program signal to be supplied to the sound reproduction system.
 20. An audio-visual display system in accordance with claim 17 wherein: the first frequency selective circuit means includes notch filter circuit means sharply tuned to the tone burst oscillation frequency for minimizing tone burst frequency components in the audio program signal before it is combined with the cue signal tone bursts; and the second frequency selective circuit means includes notch filter circuit means sharply tuned to the tone burst oscillation frequency for minimizing tone burst frequency components in the audio program signal to be supplied to the sound reproduction system.
 21. An audio-visual display system comprising: magnetic tape recorder means for recording audio program signals on magnetic tape and for reproducing same during playback of a recorded tape; at least one auxiliary display unit for producing audio effects or visual effects or both; and cue encoding means coupled to the tape recorder means for recording channel cue signals on the magnetic tape at desired points in the audio program, said cue encoding means including means for producing signals which comprise repetitive groups of at least two pulses and means for independently changing the time interval between a selected pulse and a corresponding adjacent pulse in each group to thereby provide a control channel cue signal for a control channel designated by the selected pulse further including cue decoding means coupled to the tape recorder means and to the auxiliary display unit during tape playback and responsive to a reproduced control channel cue signal for automatically controlling the auxiliary display unit in step with the playback of the recorded audio program signals. 